Ok, to get this straight, I want something that has under 230 duration and below .600 lift, correct?

What LSA should I aim for (more chop = better)?

Also, how do I determine what the valve to piston clearance will be? What is the minimum I should accept? Is there room to factor in carbon deposit?

 

I'd personally shoot for something below 230 duration on intake, and right around 230 duration exhaust. below .600 lift is better for valvetrain stability and won't require super heavy springs.

LESS LSA = more chop. 110 is probably the lowest you'll find, and that's some serious chop...the cam you referenced in your initial post had a 110 LSA. 112 is a bit more of a balance, most cams in the duration we're recommending are 113+

LSA does more than just add chop, it also shifts the power band. Less LSA means a lower power band. It's why a lot of the "smaller" cams run higher LSA because the less duration keeps the powerband lower. BIG cams usually run low LSA to shift the power band down to be more attainable. I don't think you'd want to go lower than 112 LSA with a cam below 230 duration.

Duration is what determines PTV clearance. Under 230 and you won't have to worry about it with stock heads. Significantly over that, or seriously milled heads, and you'll need to check...and the only way to check is pop the heads off.

 

Here's a great read. https://www.enginelabs.com/engine-te...-relationship/

 

That sounds counter intuitive. Why do racecars have massive chop? Shouldn't they have tight LSA to maximize high RPM?

For the duration, ok, somewhere around 228/230, .600@ .050 lift. Can I keep the stock rockers?

Ignoring the want for the chop, what would be the ideal LSA for my application?

With the trans am engine I had, I've been told that I should have gotten a higher compression to maximise the benefits of the cam. Do I end up not having an optimal cylinder pressure with a 228/230 cam or just pulling up a bit more timing advance will make up for it?

As a bonus question, if I want to move up the redline, is the limit in the valvetrain or in the bottom end? (Both?)

Thank you, I'll read the whole thing tonight.

 

Not sure about racecars...my guess is that they run massive duration cams, and need to run a super wide LSA to keep the power band accessible. I'm probably wrong.

I'd say ideal LSA for the cams you're looking at is 112-114.

More compression is always good...but it's a balance. More compression means higher octane fuel, etc. You'll certainly gain more power with more compression, but is it necessary for the cam to perform at it's best? No. HEADS I think are far more important.

How high are you looking to rev the engine? Valve train stability is the biggest thing, but the bottom end plays a part absolutely. Mine revs to 7k without issue (I have the limiter set at 6,850 because it feels "safer" to me and that's just past peak power at 6,700). Appropriately matched springs to the cam are what matters...and you'd want it all to be as light as possible. Stock rockers are fine BUT you'll want to upgrade the trunnion bearings. Many upgrade to brass bushings (myself included).

 

Makes sense. My Trans Am had 245 duration, so that is probably why it was chopping like hell.


Sorry, I didn't explain my question correctly. I will make some assumptions based on the knowledge I have acquired online in the last couple years, so correct me if I am wrong. Higher duration cams allow more air to escape during the compression stroke as the intake valve stay open for longer. To compensate for that, you can increase compression to increase cylinder pressure and gain back some efficiency. You get less air escaping at higher RPM, but since you are spinning fast, you get more turbulence in the chamber, decreasing the chance of pre-ignition. Am I correct there?

Heads will happen when I redo the entire engine at a later time.

Trunion will be done along the cam.

How fast do I want to spin it? I'd love to go all the way up to 8000 RPM, but that won't happen with this engine. That is why I want to do a full build at some point in the future.

Basically, I am going after 2 things here, and it is probably my mistake. More power by moving the RPM band up a bit and getting a different engine "personality". I've always lusted after a choppy, high RPM screamer NASCAR style V8 for a maximum amount of bald eagles.

If I have to make a choice, power and reliability will take precedence over everything else.

 

Guys, just out of curiosity, what kind of specs is this guy running?

 

Carbon? WHAT carbon?? Not many built LS motors have carbon deposit buildup problems!!! Ask me how I know!!!!! LOL-Seriously, cam lift, duration, and lobe separation angle has less to do with the numbers than they do with cubic inch displacement. In other words, are you going with a 5.7, 6.0, 6.2, 6.3 (383), 402, 427, etc., etc.. I had a .650 lift, 238° duration intake, 242 duration exhaust, on a 112 LSA. It ran pretty smooth-Because it was in an LS7. If it was in an LS6, it probably would be pretty hairy. The bigger an engine is, the more cam it can handle. IMHO, 230 I, 234 ex, .585-.600 lift on a 112 or 114 LSA would be fine in 383 or 402. If sticking with 5.7, I agree with these guys-Stay a little under 230°intake/234°exhaust. A .600 lift 228/232 on a 114 LSA should lope decent in a 5.7, and make a lot of power. Personally, I like Futral cams, FWIW. But your decision really depends a lot on C.I.D..

 

LSA is not really a good indicator of cam "size." People treat it as an indicator of overlap, which does have a profound effect, but you can't know the overlap from LSA alone, because two cams that have the same LSA will have different amounts of overlap if the lobe sizes are different. Bigger lobes will have more overlap for a given LSA.

Playing with this calculator might help:
https://mgispeedware.com/camshaft-calculator/

More overlap = rowdier idle, and more power (all other things being equal). I read a fairly well-respected tuner says that you can up to about 7 degrees of overlap in a street car (at 5.7 liters) before driveability starts to become a problem. I went with 9, and I suspect he's right. It's lurchy in first gear up to about 1500 RPM. Totally smooth in higher gears though. 232/234 @ 112, +4. But it's lots of fun on the track so I'm not complaining. Idle is pretty tame, but I've heard lopey idles from the same cam so I think the tune has a lot to do with it.

 

Mine is stock aside of a catch can.


The goal here is to take a stock LS6 and just swap the cam. While I am there, I'll be upgrading trunnion bearings and oil pump. Not even taking the heads out.

The main reason I want to do this is strictly because I miss having a mean idle. I just don't want to have an engine that perform worse or have a significantly worse gas mileage as I drive this thing quite often.

I will eventually do a better engine build, but I have chassis and brake upgrades to do first.

 

I am fully aware of that. Overlap is mostly a mix of duration and LSA. If you have a small duration cam with a tight LSA, you might have no overlap. A medium LSA and very long duration may still give you overlap.

Cool tool, thanks!

Ok, I'll do some research with tuning. I plan on buying HPTuners this winter anyway, so I should be able to do some experiments.

 

If you want to play with tuning, cheap, consider PCM Hammer (http://pcmhammer.org) or LS Droid (http://ls-droid.com), plus a $50 ObdLink ScanTool LX. Plus a copy of Tuner Pro (http://tunerpro.net). The ScanTool is the only thing that isn't free.

PCM Hammer only works with the 411 / P01 PCMs (which are in your 2002 and mine as well), but P59 support is in the works (2003-2004) and LS Droid does P59s already.

There's no free data logger yet, which is a rather glaring omission, but I hope to change that in a few months.

 

If you want a cam only and then build a monster. I'd be temped to go with a used cam. Further my 232/236 112+2 doesn't sound much different from my friend's 227/232 113+4. Compression, LSA, and tuning can noticeably change idle.

A used cam which I believe would be a solid choice for your goals. Disclaimer, I don't know the seller.
https://ls1tech.com/forums/market/1924321

 

All this stuff is free? That sounds too good to be true lol.

I'll take a look at it. Thanks!